1. Field of the Invention
The invention relates generally to mechanisms employed to raise and lower groupings of luminaires mounted to a support ring and positionable at a distal end of a high mast such as is useful for illumination of a roadway or the like, the invention particularly relating to a latching mechanism and a latch pin forming a portion thereof and which functions to minimize the potential for damage to the pin and mechanism and to reduce the potential for jamming of the mechanism.
2. Description of the Prior Art
Clusters of luminaires intended for outdoor illumination have long been mounted to support rings for hoisting of the resulting luminaire and support ring assembly to or near the top of a high mast, typically through use of a winch and hoisting cables, the assembly being necessarily lowered subsequently for maintenance, repair or even replacement of the luminaires. In accomplishing these functions, the support ring carrying the luminaires must be mounted for movement along the mast between a lowermost position necessary for servicing and the like and an operational uppermost position at or near the top of the mast at which the luminaire-bearing support ring is latched to a support permanently located at an upper portion of the mast. Latching mechanisms are typically employed for positively holding the support ring to the support at the uppermost position, a first portion of the latching mechanism being typically carried by the support ring with a second portion of said latching mechanism being carried by the support and mateable with said first portion of the latching mechanism to mutually and automatically engage on completion of a hoisting operation and to releasably latch the support ring to the stationary support. When desired, the latching mechanism must be capable of disengagement to allow the luminaire-bearing support ring to be lowered back to the ground, that is, the lowermost position.
Prior systems employed for providing the functions thus described vary in structure and operation as will be discussed hereinafter, certain of these prior systems having disadvantages and limitations resulting in jamming of latch pins and latch cams during the raising of a luminaire-bearing assembly, such jamming having the potential to occur as at least certain prior art latch pins enter at least certain prior art latch cams. The jamming of such latch pins and latch cams prevents secure engagement between a support ring bearing luminaires and an essentially stationary support mounted to a mast at or near an upper end thereof. Such a malfunction is difficult to correct in light of the fact that the jammed latching mechanism is located at a distance above ground level inconvenient for correction of the difficulty. Further, latch pins configured according to at least certain prior art designs can be bent and thus damaged during lowering of a luminaire-bearing support ring if the support ring tilts relative to the mast, such a condition being usually caused by the hanging up of the support ring on a single pin to the stationary support located at the top of a mast. Such a condition is not only difficult to correct, it usually results in damage to at least one of the prior art latch pins, thereby necessitating replacement of one or more of the latch pins with an attendant cost of labor and materials.
The art is replete with systems proposed for use and actually used for the raising and lower of luminaire assemblies relative to high mast poles, such systems being intended at least in part to address deficiencies existing in the art such as are alluded to hereinabove. Typical prior art systems include that system described by Murray et al in U.S. Pat. No. 4,234,165, in which hoist cables and a winch cable are secured to a transition plate located inside a pole by rotatable ball bearing devices intended to prevent twisting of said cables during raising and lowering operations. Luminaires are raised and lowered according to the teachings of Garchinsky in U.S. Pat. No. 4,228,488 by means of a floating linkage intended to compensate for differences in cable length, latching structure being also provided for removing loading from cables on engagement of a luminaire-bearing carrier ring with a support mounted at an upper end of a high mast. Latimer, in U.S. Pat. No. 5,975,726, discloses a high mast lighting system having a latch member adapted to latch a luminaire-bearing ring to a stationary structure disposed at an upper end of a mast on raising of the ring and to release said ring from the stationary structure to permit lowering of the ring. Blahut, in U.S. Pat. No. 4,115,845, discloses latching mechanisms intended to permit raising and lowering of a cluster of luminaires relative to a mast. In U.S. Pat. No. 4,237,530, Murray et al disclose a locking and support mechanism intended to support a platform carrying luminaires independently of cable operable for raising and lowering said luminaires. Garchinsky, in U.S. Pat. Nos. 4,149,230 and 4,429,355, further describes raising and lowering devices for luminaire assemblies mountable to high masts. In U.S. Pat. No. 3,801,813, Kichn describes a system for hoisting an assembly of luminaires to an operative position atop a high mast as does Richter in U.S. Pat. No. 6,261,122 and Thompson in U.S. Pat. No. 4,139,884. Butterworth in U.S. Pat. No. 5,570,546 describes a system having similar hoisting capabilities for raising and lowering communication equipment on a high mast. Zeller, in U.S. Pat. Nos. 3,721,816 and 3,847,333, discloses methods and apparatus for positioning a support ring carrying a cluster of luminaires on a high mast, the support ring being movable along the mast. Pletcher et al, in U.S. Pat. No. 4,198,022, disclose method and apparatus for displacing a luminaire-bearing support along a high mast.
While systems used in the prior art exhibit in a number of configurations an ability to provide useful functions, the art has experienced a long-felt need for a system particularly resistant to jamming on raising of a luminaire-bearing support to an operational position atop a high mast and further resistant to damage to latching structure on disengagement of such a support to lower said support for service. The present invention therefore intends the provision of a latch mechanism and particularly an improved latch pin capable of an articulating attachment to a luminaire-hearing support ring so that damage to the pin is prevented in the event of improper operation of a lowering device. Further, the present latch pin is capable of providing a centering function to prevent misalignment of said pin relative to cam latch structure carried on a stationary mount disposed atop a high mast, thereby preventing jamming between the pin and cam latch structure. The present latch mechanism thus addresses needs existing in at least certain prior art systems by providing inter alia an improved and reliable latch pin that further permits economies of cost in the construction of a system used in environments within which the invention is intended to function.